The no-reflow lesion in brain occurs after circulatory arrest, can be quantified, and may be related to the appearance of neurological damage after circulatory arrest. The purpose of our work is to study the relationship of the no-reflow lesion to circulatory arrest during hypothermia and after treatment with certain drugs. We also correlate the severity of no-reflow lesions after periods of hypothermic circulatory arrest with cerebral hemodynamics and metabolism. We ultimately hope to demonstrate a causal relationship between the no-reflow lesion and neurological damage, using several approaches to attack this difficult question. Bibliographic references: (1) Castaneda, A.R., Lamberti, J., Sade, R.M., Williams, R.G., Nadas, A.S.: Open heart surgery during the first three months of life. J. Thorac. Cardiovasc. Surg. 68:719-731, 1974.